<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script>
  </head>
  <body>
    <div id="root">
      <h2>今天天气很{{info}}</h2>
      <button @click="isHot = !isHot">点我切换天气</button>
    </div>

    <script>
      const vm = new Vue({
        el: "#root",
        data: {
          isHot: true,
        },
        computed: {
          info() {
            return this.isHot ? "炎热" : "凉爽";
          },
        },
        methods: {
          //   change() {
          //     this.isHot = !this.isHot;
          //   },
        },
        // watch: {
        //   isHot: {
        //     immediate: true,
        //     //当isHot发生改变时
        //     handler(cur, pre) {
        //         console.log(pre);
        //         console.log('isHot发生改变');
        //         console.log(cur);
        //     },
        //   },
        // },
      });

      vm.$watch('isHot', {
          immediate: true,
          handler(cur, pre) {
              console.log('isHot被修改了', cur, pre);
          }
      })
    </script>
  </body>
</html>
